WO2016117676A1 - Filter device - Google Patents

Filter device Download PDF

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Publication number
WO2016117676A1
WO2016117676A1 PCT/JP2016/051825 JP2016051825W WO2016117676A1 WO 2016117676 A1 WO2016117676 A1 WO 2016117676A1 JP 2016051825 W JP2016051825 W JP 2016051825W WO 2016117676 A1 WO2016117676 A1 WO 2016117676A1
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WO
WIPO (PCT)
Prior art keywords
filter
filter circuit
resonator
signal line
acoustic
Prior art date
Application number
PCT/JP2016/051825
Other languages
French (fr)
Japanese (ja)
Inventor
浩司 野阪
Original Assignee
株式会社村田製作所
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 株式会社村田製作所 filed Critical 株式会社村田製作所
Priority to DE112016000452.4T priority Critical patent/DE112016000452B4/en
Priority to CN201680006094.0A priority patent/CN107210733B/en
Priority to JP2016570717A priority patent/JP6432610B2/en
Priority to KR1020177020191A priority patent/KR101944652B1/en
Publication of WO2016117676A1 publication Critical patent/WO2016117676A1/en
Priority to US15/633,850 priority patent/US10158341B2/en

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/64—Filters using surface acoustic waves
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/70—Multiple-port networks for connecting several sources or loads, working on different frequencies or frequency bands, to a common load or source
    • H03H9/72—Networks using surface acoustic waves
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/01—Frequency selective two-port networks
    • H03H7/12—Bandpass or bandstop filters with adjustable bandwidth and fixed centre frequency
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/01—Frequency selective two-port networks
    • H03H7/17—Structural details of sub-circuits of frequency selective networks
    • H03H7/1741—Comprising typical LC combinations, irrespective of presence and location of additional resistors
    • H03H7/175—Series LC in series path
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/64—Filters using surface acoustic waves
    • H03H9/6423—Means for obtaining a particular transfer characteristic
    • H03H9/6433—Coupled resonator filters
    • H03H9/6483—Ladder SAW filters
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/70—Multiple-port networks for connecting several sources or loads, working on different frequencies or frequency bands, to a common load or source

Definitions

  • the present invention relates to a filter device having first to third filter circuits connected to a common terminal.
  • Patent Document 1 discloses a third branching filter in which first to third filters F1 to F3 are connected to an antenna terminal.
  • the first filter F1 is a low-pass filter whose pass band is the first frequency band and whose attenuation bands are the second and third frequency bands.
  • the second filter F2 uses the second frequency band as a pass band, and uses the first and third frequency bands as attenuation bands.
  • the second filter F2 is a bandpass filter having a SAW filter.
  • the third filter F3 is composed of an LC filter, and has a third frequency band as a pass band and first and second frequency bands as attenuation bands.
  • first to third filters F1 to F3 are commonly connected to antenna terminals. Therefore, an impedance matching circuit has to be provided on the first and third filter side composed of the LC filter.
  • An object of the present invention is to provide a filter device that can omit an impedance matching circuit.
  • the filter device includes a first filter circuit which is a low-pass filter having a common terminal and a first signal line connected to the common terminal and having a first passband, A second signal line connected to a common terminal; and a second pass band located on a higher frequency side than the first pass band of the first filter circuit. And a second filter circuit that is a bandpass filter and a third signal line connected to the common terminal, the band being higher than the second passband of the second filter circuit And a third filter circuit having a third passband located on the side, wherein the first filter circuit is disposed closest to the common terminal in the first signal line.
  • the second filter circuit is disposed closest to the common terminal in the second signal line
  • the third filter circuit includes a third acoustic resonator disposed closest to the common terminal in the third signal line.
  • the first filter circuit has a first acoustic resonator having an anti-resonance frequency and a resonance frequency located in the second passband; A second capacitive element connected to the first signal line and a ground potential; In this case, the attenuation amount in the second pass band can be sufficiently increased in the first filter circuit.
  • the second signal of the first filter circuit is an acoustic resonator
  • the second filter circuit is a series arm.
  • a parallel arm connecting a line and a ground potential, an acoustic resonator is disposed on the parallel arm, and the acoustic resonator constituting the second capacitor element of the first filter circuit; and
  • the resonance frequency of the acoustic resonator disposed on the parallel arm of the second filter circuit is substantially the same as the resonance frequency of the second acoustic resonator.
  • the loss can be further reduced, and the attenuation in the vicinity of the passband can be further increased in each of the first to third filter circuits.
  • the second acoustic resonator, the acoustic resonator and the second filter constituting the second capacitive element of the first filter circuit.
  • Resonant frequencies of the acoustic resonators arranged on the parallel arms of the circuit are within an average value ⁇ 5% of resonance frequencies of these acoustic resonators.
  • the loss can be further reduced, and the attenuation in the vicinity of the passband can be further increased in each of the first to third filter circuits.
  • the second filter circuit is connected to a parallel arm that connects the second acoustic resonator, the second signal line, and a ground potential. It is a ladder type filter which has the 4th acoustic resonator provided. In this case, the steepness of the filter characteristics in the second filter circuit can be enhanced.
  • the third filter circuit includes a second inductor connected between the third signal line and a ground potential, and the second inductor.
  • This is an LC filter having a third capacitor element connected in series. In this case, the size of the third filter circuit can be reduced.
  • the third filter circuit may be a band-pass filter.
  • a signal in a specific frequency band can be reliably transmitted or received by the third filter circuit.
  • the band-pass filter a ladder type filter is preferably used. In that case, the steepness of the filter characteristic in the third filter circuit can be enhanced.
  • At least one of the first to third acoustic resonators is an elastic wave resonator.
  • the steepness of the filter characteristics can be further enhanced.
  • a surface acoustic wave resonator is preferably used. When the surface acoustic wave resonator is used, the steepness of the filter characteristics can be further effectively improved.
  • the first capacitive element is an acoustic resonator.
  • the first capacitive element may be configured using the capacitance of the acoustic resonator. In this case, the amount of attenuation can be increased by setting the resonance frequency of the acoustic resonator to the attenuation band.
  • the impedance matching circuit can be omitted in the configuration in which the first to third filter circuits are connected to the common terminal.
  • FIG. 1 is a circuit diagram of a filter device according to a first embodiment of the present invention.
  • FIG. 2 is a diagram illustrating the filter characteristics of the first filter circuit of the filter device according to the first embodiment.
  • FIG. 3 is a diagram illustrating the filter characteristics of the second filter circuit of the filter device according to the first embodiment.
  • FIG. 4 is a diagram illustrating the filter characteristics of the third filter circuit of the filter device according to the first embodiment.
  • FIG. 5 is a circuit diagram of a filter device according to the second embodiment of the present invention.
  • FIG. 6 is a circuit diagram of a filter device according to the third embodiment of the present invention.
  • FIG. 7 is a front sectional view showing a surface acoustic wave resonator as an example of an acoustic resonator.
  • FIG. 1 is a circuit diagram of a filter device according to a first embodiment of the present invention.
  • the filter device 1 has a common terminal 2. One end of the first to third filter circuits F1 to F3 is commonly connected to the common terminal 2.
  • the first filter circuits F1 to F3 have the following first to third passbands f1 to f3, respectively.
  • F1 Low band cellular band, 699 MHz to 960 MHz.
  • F2 GPS, GLONASS and BEIDOU bands, 1559 MHz to 1608 MHz.
  • F3 Middle band cellular band, 1700 MHz to 2170 MHz.
  • the first filter circuit F1 is a low-pass filter having an LC resonator and an acoustic resonator.
  • the first filter circuit F1 has the first pass band f1 that is the low-band cellular band, but is a low-pass filter, and therefore passes signals in a band of 960 MHz or less. That is, the first pass band f1 is set so as to pass the low band cellular band of 699 to 960 MHz.
  • the second filter circuit F2 is a bandpass filter made of an acoustic resonator, and is made of a ladder type filter.
  • the third filter circuit F3 is a high-pass filter having an LC resonator and an acoustic resonator.
  • the third filter circuit F3 is a high-pass filter, and passes a signal having a frequency of 1700 MHz or higher which is the lower limit of the third passband f3.
  • the first filter circuit F1 has a first signal line 4 connecting the common terminal 2 and the first terminal 3.
  • a plurality of first inductors 5 a to 5 c are provided on the first signal line 4.
  • the plurality of first inductors 5 a to 5 c are connected in series in the first signal line 4.
  • the first capacitive elements 6a to 6c are connected in parallel to the first inductors 5a to 5c, respectively. Further, a second capacitance element 7a for impedance adjustment is connected between a connection point between the first inductor 5a and the first inductor 5b and the ground potential. The second capacitive element 7a is a capacitor. An inductor 8 is connected in series with the second capacitor element 7a for impedance adjustment. A first acoustic resonator is connected as a second capacitive element 7b between a connection point between the first inductor 5b and the first inductor 5c and the ground potential.
  • the first acoustic resonator as the second capacitive element 7b has a resonance frequency and an anti-resonance frequency.
  • the second capacitor element 7b is formed of a surface acoustic wave resonator.
  • a surface acoustic wave resonator is used as the second capacitive element 7b by utilizing the capacitance of the surface acoustic wave resonator.
  • a first acoustic resonator similar to the second capacitive element 7b is connected as the second capacitive element 7c between the connection point between the first inductor 5c and the first terminal 3 and the ground potential. Has been.
  • the element closest to the common terminal 2 is the first inductor 5a.
  • the second capacitance elements 7a to 7c are impedance adjustment capacitance elements.
  • the two second capacitive elements 7b and 7c are composed of the first acoustic resonator as described above, and the resonance frequency is located in the pass band f2 of the second filter circuit F2. Therefore, the signal in the pass band of the second filter circuit F2 can be released to the ground potential side.
  • the second filter circuit F2 has a second signal line 10 connecting the common terminal 2 and the second terminal 9.
  • series arm resonators S1, S2, S3, S4, and S5 are provided in order from the common terminal 2 side. That is, the second signal line 10 constitutes a series arm, and the series arm resonators S1 to S5 are connected in series in this series arm.
  • the series arm resonators S1 to S5 are composed of surface acoustic wave resonators.
  • the series arm resonators S1 to S5 correspond to a second acoustic resonator having a resonance frequency and an anti-resonance frequency.
  • the parallel arm resonator P1 is provided on the parallel arm connecting the connection point between the series arm resonator S1 and the series arm resonator S2 and the ground potential.
  • the parallel arm resonator P2 is provided on the parallel arm that connects the connection point between the series arm resonator S2 and the series arm resonator S3 and the ground potential.
  • the parallel arm resonator P3 is provided on the parallel arm that connects the connection point between the series arm resonator S3 and the series arm resonator S4 and the ground potential.
  • a parallel arm resonator P4 is provided on the parallel arm connecting the connection point between the series arm resonator S4 and the series arm resonator S5 and the ground potential.
  • the parallel arm resonators P1 to P4 are also composed of surface acoustic wave resonators.
  • the second filter circuit F2 is a ladder filter having the series arm resonators S1 to S5 and the parallel arm resonators P1 to P4.
  • the second filter circuit F2 is a band pass filter, and the center frequency of the pass band is located in the above-described pass band f2.
  • the resonance frequencies of the series arm resonators S1 to S5 are in the passband f2, and the antiresonance frequencies of the parallel arm resonators P1 to P4 are in the passband f2.
  • the element closest to the common terminal 2 in the second signal line 10 is the second acoustic resonator which is the series arm resonator S1.
  • the third filter circuit F3 has a third signal line 12 connecting the common terminal 2 and the third terminal 11.
  • a low pass filter 21 is connected between the third filter circuit F 3 and the third terminal 11.
  • the third filter circuit F3 is a high-pass filter.
  • the third filter circuit F3 and the low-pass filter 21 are connected in series. Therefore, the third filter circuit F3 and the low-pass filter 21 form a pass band.
  • third acoustic resonators 13 a to 13 c are provided on the third signal line 12.
  • the plurality of third acoustic resonators 13 a to 13 c are connected to each other in series on the third signal line 12.
  • the third inductor 14a and the third capacitive element 15a are connected in series between the connection point between the third acoustic resonator 13a and the third acoustic resonator 13b and the ground potential.
  • the third inductor 14b and the third capacitive element 15b are connected in series between the connection point between the third acoustic resonator 13b and the third acoustic resonator 13c and the ground potential. ing.
  • the element closest to the common terminal 2 is the third acoustic resonator 13a.
  • the element closest to the common terminal 2 is the first inductor 5a, and is closest to the common terminal 2 of the second filter circuit F2 and the third filter circuit F3.
  • the elements are second and third acoustic resonators, respectively, and these elements are arranged on the signal line. Therefore, the impedance matching circuit on the common terminal 2 side of the first and third filter circuits F1 and F3 made of LC filters and the second filter circuit F2 using the acoustic resonator can be omitted.
  • the anti-resonance frequency of the third acoustic resonators 13a to 13c of the third filter circuit F3 is located in the pass band f2 of the second filter circuit F2.
  • a trap can be formed in the pass band f2 in the filter characteristics of the third filter circuit F3.
  • the low-pass filter 21 includes fourth inductors 22 a and 22 b provided on the third signal line 12. Fourth capacitive elements 23a and 23b are connected in parallel to the fourth inductors 22a and 22b, respectively.
  • a fifth capacitor 24a is connected between the end of the fourth inductor 22a on the third filter circuit F3 side and the ground potential.
  • the fifth capacitive element 24b is connected between the connection point between the fourth inductor 22a and the fourth inductor 22b and the ground potential.
  • a fifth capacitive element 24c is connected between the connection point between the fourth inductor 22b and the third terminal 11 and the ground potential.
  • the fifth capacitive elements 24a to 24c are made of acoustic resonators and have a resonance frequency and an anti-resonance frequency.
  • the low-pass filter 21 is not necessarily provided, but by providing the low-pass filter 21, a pass band can be formed as described above.
  • the resonance frequency of the fifth capacitive elements 24a to 24c is positioned in the pass band f2 of the second filter circuit F2.
  • the attenuation in the second pass band can be further increased.
  • the second capacitive elements 7b and 7c constituted by acoustic resonators, the series arm resonators S1 to S5, the parallel arm resonators P1 to P4, and the third filter used in the second filter circuit F2. It is desirable that all the acoustic resonators constituting the third acoustic resonators 13a to 13c and the fifth capacitive elements 24a to 24c used in the circuit F3 have substantially the same resonance frequency and antiresonance frequency. As a result, the types of acoustic resonators can be reduced, the cost can be reduced, and the piezoelectric substrate or the like constituting the filter device 1 can be shared. Therefore, the filter device 1 can be downsized. In particular, the first to third filter circuits F1 to F3 can be configured using the same piezoelectric body.
  • the second capacitive element of the first filter circuit is formed of an acoustic resonator
  • the second filter circuit has a parallel arm that connects the second signal line, which is a serial arm, and a ground potential, and is connected in parallel.
  • An acoustic resonator is arranged on the arm, and the resonance frequency of the acoustic resonator constituting the second capacitive element of the first filter circuit and the acoustic resonator arranged on the parallel arm of the second filter circuit Is substantially the same as the resonance frequency of the second acoustic resonator.
  • each of the second acoustic resonator, the acoustic resonator constituting the second capacitive element of the first filter circuit, and the acoustic resonator disposed in the parallel arm of the second filter circuit The resonance frequency is in the range of the average value ⁇ 5% of the resonance frequencies of these acoustic resonators.
  • FIG. 2 shows the filter characteristics of the first filter circuit F1
  • FIG. 3 shows the filter characteristics of the second filter circuit
  • FIG. 4 shows the filter characteristics of the third filter circuit F3.
  • the attenuation amount is small in the first pass band f1.
  • the amount of attenuation is sufficiently large.
  • an arrow A below the second passband f2 indicates the position of the trap due to the antiresonance frequency of the acoustic resonator used as the second capacitive elements 7b and 7c in the first filter circuit. That is, since the antiresonance frequency of the acoustic resonator as the second capacitive elements 7b and 7c is located at the frequency indicated by the arrow A, it is possible to sufficiently increase the attenuation in the second passband f2. .
  • the second capacitive elements 7b and 7c are made of acoustic resonators, but at least one first capacitive element is made of an acoustic resonator. It only has to be done.
  • the attenuation amount of the second passband f2 is sufficiently small.
  • a sufficiently large attenuation is obtained in the first passband f1 and the third passband f3.
  • This pass band is obtained by the characteristics of the second filter circuit F2 as a band pass filter.
  • the resonance frequency of the series arm resonators S1 to S5 and the antiresonance frequency of the parallel arm resonators P1 to P4 are located in the position indicated by the arrow B, that is, in the passband f2. Yes. Further, the frequency position characteristic indicated by the arrow C indicates the attenuation pole due to the resonance frequency of the parallel arm resonators P1 to P4. Arrow D indicates the attenuation pole due to the antiresonance frequency of the series arm resonators S1 to S5.
  • the resonance frequencies of the series arm resonators S1 to S5 and the parallel arm resonators are used.
  • the antiresonance frequencies P1 to P4 are positions indicated by arrows B.
  • the series arm resonators S1 to S5 and the parallel arm resonators P1 to P4 made of acoustic resonators do not necessarily have substantially the same resonance frequency and antiresonance frequency.
  • the attenuation is sufficiently small in the third passband f3.
  • a sufficiently large attenuation is obtained in the first passband f1 and the second passband f2. That is, the attenuation amount in the first pass band f1 is sufficiently large due to the characteristics as a high-pass filter.
  • the attenuation in the second pass band f2 is due to the antiresonance frequencies of the third acoustic resonators 13a to 13c being located in the pass band f2, as indicated by the arrow E. Thereby, it is possible to sufficiently increase the attenuation in the second passband f2.
  • the low-pass filter 21 since the low-pass filter 21 is connected, the amount of attenuation gradually increases on the higher frequency side than the third passband f3.
  • the resonance frequency of each acoustic resonator as the fifth capacitive elements 24a to 24c is located at the frequency indicated by the arrow F. Therefore, it is possible to form a trap at the frequency position indicated by the arrow F on the high frequency side of the third passband f3. Therefore, traps with sufficiently large attenuation can be formed on the low frequency side and high frequency side of the third passband f3, and the selectivity can be increased.
  • the acoustic resonators as the fifth capacitive elements 24a to 24c are provided to form the trap. However, if at least one acoustic resonator is provided, the trap can be formed. .
  • the third filter circuit F3 only needs to include the third acoustic resonator 13a closest to the common terminal 2 among the third acoustic resonators 13a to 13c.
  • the third acoustic resonators 13b and 13c may be omitted.
  • the second capacitor element 7b is formed of a surface acoustic wave resonator.
  • the structure of such a surface acoustic wave resonator is not particularly limited.
  • a surface acoustic wave resonator 31 shown in FIG. 7 can be used.
  • an IDT electrode 33 is provided on a piezoelectric substrate 32.
  • a dielectric film 34 made of SiO 2 is provided so as to cover the IDT electrode 33.
  • the frequency position of the resonance frequency and the anti-resonance frequency can be adjusted by adjusting the metal constituting the IDT electrode and the film thickness.
  • the surface acoustic wave resonator is shown as an acoustic resonator.
  • an acoustic resonator other than the surface acoustic wave resonator may be used.
  • a boundary acoustic wave resonator may be used.
  • a BAW resonator using a bulk wave propagating through the piezoelectric thin film may be used.
  • a piezoelectric resonator using a single piezoelectric substrate or a laminated piezoelectric material may be used.
  • FIG. 5 is a circuit diagram of a filter device according to the second embodiment of the present invention.
  • the first capacitive elements 6a to 6c are acoustic resonators.
  • a second capacitive element 7d made of an acoustic resonator is connected between a connection point between the first inductor 5a and the first inductor 5b and the ground potential.
  • the third capacitive elements 15c and 15d are made of acoustic resonators.
  • the filter device 41 is configured in the same manner as the filter device 1.
  • the first capacitive elements 6a to 6c as described above may be constituted by acoustic resonators, and in the first filter circuit F1, capacitors arranged on the line connecting the first signal line 4 and the ground potential. All the elements may be acoustic resonators.
  • acoustic resonators may be used as the fifth capacitive elements 24a to 24c on the line connecting the third signal line 12 and the ground potential.
  • the filter device 41 has the same effects as the filter device 1.
  • the anti-resonance frequency is positioned in the second pass band f2, so that the second resonator in the second pass band f2
  • the amount of attenuation can be increased.
  • the attenuation in the second passband f2 is further increased by positioning the antiresonance frequency in the second passband f2. Can be bigger.
  • FIG. 6 is a circuit diagram of the filter device 51 according to the third embodiment.
  • the first and second filter circuits F1, F2 are configured in the same manner as the filter device 41 of the second embodiment.
  • the difference is that the third filter circuit F3 is a band-pass filter composed of a ladder filter.
  • the series arm resonators S11 to S15 are connected in series on the third signal line 12 connecting the common terminal 2 and the third terminal 11.
  • a parallel arm resonator P11 is provided on the parallel arm connecting the connection point between the series arm resonators S11 and S12 and the ground potential.
  • a parallel arm resonator P12 is provided between the connection point between the series arm resonators S12 and S13 and the ground potential.
  • a parallel arm resonator P13 is provided between the connection point between the series arm resonators S13 and S14 and the ground potential.
  • a parallel arm resonator P14 is provided on the parallel arm connecting the connection point between the series arm resonators S14 and S15 and the ground potential.
  • an inductor 52a is connected between the connection point between the series arm resonator S11 and the series arm resonator S12 and the ground potential.
  • An inductor 52b is connected between a connection point between the series arm resonator S14 and the series arm resonator S15 and the ground potential.
  • the inductors 52a and 52b are provided to adjust the impedance.
  • the third filter circuit F3 itself may be a bandpass filter.
  • the series arm resonators S11 to S15 and the parallel arm resonators P11 to P14 are acoustic resonators having a resonance frequency and an antiresonance frequency.
  • the element closest to the common terminal 2 in the third filter circuit F3 is the series arm resonator S11. That is, the element closest to the common terminal 2 is the third acoustic resonator and is provided on the third signal line 12.
  • the element closest to the common terminal 2 in the first filter circuit F1 is the first inductor 5a provided in the first signal line 4, and the second and third filter circuits F2, F2 are provided.
  • F3 there are a series arm resonator S1 and a series arm resonator S11 made of acoustic resonators, which are provided on the second and third signal lines 10 and 12, respectively. Therefore, it is not necessary to provide an impedance matching circuit on the common terminal 2 side. Therefore, the filter device 51 can also be reduced in size and cost.
  • the first to third filter circuits F1 to F3 can be appropriately modified as will be apparent from appropriate first to third embodiments. That is, the number of filter circuits and the number of elements in the first to third filter circuits F1 to F3 are not limited to the contents of the embodiment.

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
  • Filters And Equalizers (AREA)

Abstract

Provided is a filter device which can dispense with an impedance matching circuit. This filter device 1 comprises a first through a third filter circuit F1-F3 which are connected to a common terminal 2. The first filter circuit F1 comprises a first inductor 5a, which is nearest to the common terminal 2 on a first signal line 4, and a first capacitive element 6a which is connected in parallel to the first inductor 5a. The second filter circuit F2 comprises a series arm resonator S1 which is a second acoustic resonator nearest to the common terminal 2 on a second signal line 10, and the third filter circuit F3 comprises a third acoustic resonator 13a which is arranged nearest to the common terminal 2 on a third signal line 12.

Description

フィルタ装置Filter device
　本発明は、共通端子に接続された第１～第３のフィルタ回路を有するフィルタ装置に関する。 The present invention relates to a filter device having first to third filter circuits connected to a common terminal.
　従来、携帯電話機などにおいては、周波数帯が異なる３つの信号を分波する分波器が用いられている。下記の特許文献１には、アンテナ端子に、第１～第３のフィルタＦ１～Ｆ３が接続されている３分波器が開示されている。第１のフィルタＦ１は、第１の周波数帯を通過帯域とし、第２及び第３の周波数帯を減衰帯域とするローパスフィルタである。第２のフィルタＦ２は、第２の周波数帯を通過帯域とし、第１及び第３の周波数帯を減衰帯域とする。また、第２のフィルタＦ２は、ＳＡＷフィルタを有するバンドパスフィルタである。第３のフィルタＦ３は、ＬＣフィルタからなり、第３の周波数帯を通過帯域とし、第１及び第２の周波数帯を減衰帯域とする。 Conventionally, in a mobile phone or the like, a duplexer that demultiplexes three signals having different frequency bands is used. Patent Document 1 below discloses a third branching filter in which first to third filters F1 to F3 are connected to an antenna terminal. The first filter F1 is a low-pass filter whose pass band is the first frequency band and whose attenuation bands are the second and third frequency bands. The second filter F2 uses the second frequency band as a pass band, and uses the first and third frequency bands as attenuation bands. The second filter F2 is a bandpass filter having a SAW filter. The third filter F3 is composed of an LC filter, and has a third frequency band as a pass band and first and second frequency bands as attenuation bands.
特開２００４－１９４２４０号公報JP 2004-194240 A
　特許文献１に記載の３分波器では、アンテナ端子に第１～第３のフィルタＦ１～Ｆ３が共通接続されている。そのため、ＬＣフィルタからなる第１，第３のフィルタ側に、インピーダンス整合回路を設けねばならなかった。 In the third branching filter described in Patent Document 1, first to third filters F1 to F3 are commonly connected to antenna terminals. Therefore, an impedance matching circuit has to be provided on the first and third filter side composed of the LC filter.
　本発明の目的は、インピーダンス整合回路を省略することを可能とするフィルタ装置を提供することにある。 An object of the present invention is to provide a filter device that can omit an impedance matching circuit.
　本発明に係るフィルタ装置は、共通端子と、前記共通端子に接続されている第１の信号ラインを有しており、第１の通過帯域を有するローパスフィルタである第１のフィルタ回路と、前記共通端子に接続されている第２の信号ラインを有しており、前記第１のフィルタ回路の前記第１の通過帯域よりも高域側に位置している第２の通過帯域を有しており、バンドパスフィルタである第２のフィルタ回路と、前記共通端子に接続されている第３の信号ラインを有しており、前記第２のフィルタ回路の前記第２の通過帯域よりも高域側に位置している第３の通過帯域を有する第３のフィルタ回路とを備え、前記第１のフィルタ回路が、前記第１の信号ラインにおいて、前記共通端子に最も近くに配置されている第１のインダクタと、前記第１のインダクタと並列に接続されてＬＣ共振回路を構成している第１の容量素子とを含んでおり、前記第２のフィルタ回路が、前記第２の信号ラインにおいて、前記共通端子に最も近くに配置されている第２の音響共振子を含んでおり、前記第３のフィルタ回路が、前記第３の信号ラインにおいて、前記共通端子に最も近くに配置されている第３の音響共振子を含んでいる。 The filter device according to the present invention includes a first filter circuit which is a low-pass filter having a common terminal and a first signal line connected to the common terminal and having a first passband, A second signal line connected to a common terminal; and a second pass band located on a higher frequency side than the first pass band of the first filter circuit. And a second filter circuit that is a bandpass filter and a third signal line connected to the common terminal, the band being higher than the second passband of the second filter circuit And a third filter circuit having a third passband located on the side, wherein the first filter circuit is disposed closest to the common terminal in the first signal line. 1 inductor and the first A first capacitive element connected in parallel with the inductor to form an LC resonance circuit, and the second filter circuit is disposed closest to the common terminal in the second signal line And the third filter circuit includes a third acoustic resonator disposed closest to the common terminal in the third signal line. Yes.
　本発明に係るフィルタ装置のある特定の局面によれば、前記第１のフィルタ回路が、反共振周波数と前記第２の通過帯域内に位置する共振周波数とを有する第１の音響共振子と、前記第１の信号ラインとグラウンド電位とに接続される第２の容量素子とを含んでいる。この場合には、第１のフィルタ回路において、第２の通過帯域における減衰量を十分大きくすることができる。 According to a specific aspect of the filter device according to the present invention, the first filter circuit has a first acoustic resonator having an anti-resonance frequency and a resonance frequency located in the second passband; A second capacitive element connected to the first signal line and a ground potential; In this case, the attenuation amount in the second pass band can be sufficiently increased in the first filter circuit.
　本発明に係るフィルタ装置の他の特定の局面では、前記第１のフィルタ回路の前記第２の容量素子が音響共振子からなり、前記第２のフィルタ回路が、直列腕である第２の信号ラインとグラウンド電位とを結ぶ並列腕を有し、前記並列腕に音響共振子が配置されており、前記第１のフィルタ回路の前記第２の容量素子を構成している前記音響共振子及び前記第２のフィルタ回路の前記並列腕に配置されている音響共振子の共振周波数が、前記第２の音響共振子の共振周波数とほぼ同じである。この場合には、損失をより一層低減することができ、かつ第１～第３のフィルタ回路において、それぞれ、通過帯域近傍における減衰量をより一層大きくすることができる。 In another specific aspect of the filter device according to the present invention, the second signal of the first filter circuit is an acoustic resonator, and the second filter circuit is a series arm. A parallel arm connecting a line and a ground potential, an acoustic resonator is disposed on the parallel arm, and the acoustic resonator constituting the second capacitor element of the first filter circuit; and The resonance frequency of the acoustic resonator disposed on the parallel arm of the second filter circuit is substantially the same as the resonance frequency of the second acoustic resonator. In this case, the loss can be further reduced, and the attenuation in the vicinity of the passband can be further increased in each of the first to third filter circuits.
　本発明に係るフィルタ装置の他の特定の局面では、前記第２の音響共振子、前記第１のフィルタ回路の前記第２の容量素子を構成している前記音響共振子及び前記第２のフィルタ回路の前記並列腕に配置されている音響共振子の各共振周波数が、これらの音響共振子の共振周波数の平均値±５％の範囲内にある。この場合には、損失をより一層低減することができ、かつ第１～第３のフィルタ回路において、それぞれ、通過帯域近傍における減衰量をより一層大きくすることができる。 In another specific aspect of the filter device according to the present invention, the second acoustic resonator, the acoustic resonator and the second filter constituting the second capacitive element of the first filter circuit. Resonant frequencies of the acoustic resonators arranged on the parallel arms of the circuit are within an average value ± 5% of resonance frequencies of these acoustic resonators. In this case, the loss can be further reduced, and the attenuation in the vicinity of the passband can be further increased in each of the first to third filter circuits.
　本発明に係るフィルタ装置のさらに他の特定の局面では、前記第２のフィルタ回路が、前記第２の音響共振子と、前記第２の信号ラインとグラウンド電位とを接続している並列腕に設けられた第４の音響共振子とを有する、ラダー型フィルタである。この場合には、第２のフィルタ回路におけるフィルタ特性の急峻性を高めることができる。 In still another specific aspect of the filter device according to the present invention, the second filter circuit is connected to a parallel arm that connects the second acoustic resonator, the second signal line, and a ground potential. It is a ladder type filter which has the 4th acoustic resonator provided. In this case, the steepness of the filter characteristics in the second filter circuit can be enhanced.
　本発明に係るフィルタ装置の別の特定の局面では、前記第３のフィルタ回路が、前記第３の信号ラインとグラウンド電位との間に接続された第２のインダクタと、該第２のインダクタと直列に接続された第３の容量素子とを有するＬＣフィルタである。この場合には、第３のフィルタ回路の小型化を図ることができる。 In another specific aspect of the filter device according to the present invention, the third filter circuit includes a second inductor connected between the third signal line and a ground potential, and the second inductor. This is an LC filter having a third capacitor element connected in series. In this case, the size of the third filter circuit can be reduced.
　もっとも、本発明においては、第３のフィルタ回路はバンドパスフィルタであってもよい。その場合には、第３のフィルタ回路により、特定の周波数帯の信号を確実に送信または受信することができる。上記バンドパスフィルタとしては、好ましくは、ラダー型フィルタが用いられる。その場合には、第３のフィルタ回路におけるフィルタ特性の急峻性を高めることができる。 However, in the present invention, the third filter circuit may be a band-pass filter. In that case, a signal in a specific frequency band can be reliably transmitted or received by the third filter circuit. As the band-pass filter, a ladder type filter is preferably used. In that case, the steepness of the filter characteristic in the third filter circuit can be enhanced.
　本発明に係るフィルタ装置の別の特定の局面では、前記第１～第３の音響共振子の少なくとも１つが、弾性波共振子である。この場合には、フィルタ特性の急峻性をより一層高めることができる。弾性波共振子としては、弾性表面波共振子が好適に用いられる。弾性表面波共振子を用いた場合には、フィルタ特性の急峻性をより一層効果的に高めることができる。 In another specific aspect of the filter device according to the present invention, at least one of the first to third acoustic resonators is an elastic wave resonator. In this case, the steepness of the filter characteristics can be further enhanced. As the acoustic wave resonator, a surface acoustic wave resonator is preferably used. When the surface acoustic wave resonator is used, the steepness of the filter characteristics can be further effectively improved.
　本発明に係るフィルタ装置のさらに他の特定の局面では、前記第１の容量素子が、音響共振子からなる。このように、音響共振子の容量を利用して第１の容量素子を構成してもよい。この場合には、音響共振子の共振周波数を、減衰帯域に設定することにより、減衰量の拡大を図ることも可能となる。 In still another specific aspect of the filter device according to the present invention, the first capacitive element is an acoustic resonator. As described above, the first capacitive element may be configured using the capacitance of the acoustic resonator. In this case, the amount of attenuation can be increased by setting the resonance frequency of the acoustic resonator to the attenuation band.
　本発明に係るフィルタ装置によれば、共通端子に第１～第３のフィルタ回路が接続されている構成において、インピーダンス整合回路を省略することが可能となる。 According to the filter device of the present invention, the impedance matching circuit can be omitted in the configuration in which the first to third filter circuits are connected to the common terminal.
図１は、本発明の第１の実施形態に係るフィルタ装置の回路図である。FIG. 1 is a circuit diagram of a filter device according to a first embodiment of the present invention. 図２は、第１の実施形態のフィルタ装置の第１のフィルタ回路のフィルタ特性を示す図である。FIG. 2 is a diagram illustrating the filter characteristics of the first filter circuit of the filter device according to the first embodiment. 図３は、第１の実施形態のフィルタ装置の第２のフィルタ回路のフィルタ特性を示す図である。FIG. 3 is a diagram illustrating the filter characteristics of the second filter circuit of the filter device according to the first embodiment. 図４は、第１の実施形態のフィルタ装置の第３のフィルタ回路のフィルタ特性を示す図である。FIG. 4 is a diagram illustrating the filter characteristics of the third filter circuit of the filter device according to the first embodiment. 図５は、本発明の第２の実施形態に係るフィルタ装置の回路図である。FIG. 5 is a circuit diagram of a filter device according to the second embodiment of the present invention. 図６は、本発明の第３の実施形態に係るフィルタ装置の回路図である。FIG. 6 is a circuit diagram of a filter device according to the third embodiment of the present invention. 図７は、音響共振子の一例としての弾性表面波共振子を示す正面断面図である。FIG. 7 is a front sectional view showing a surface acoustic wave resonator as an example of an acoustic resonator.
　以下、図面を参照しつつ、本発明の具体的な実施形態を説明することにより、本発明を明らかにする。 Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.
　なお、本明細書に記載の各実施形態は、例示的なものであり、異なる実施形態間において、構成の部分的な置換または組み合わせが可能であることを指摘しておく。 It should be pointed out that each embodiment described in this specification is an example, and a partial replacement or combination of configurations is possible between different embodiments.
　図１は、本発明の第１の実施形態に係るフィルタ装置の回路図である。 FIG. 1 is a circuit diagram of a filter device according to a first embodiment of the present invention.
　フィルタ装置１は、共通端子２を有する。共通端子２に、第１～第３のフィルタ回路Ｆ１～Ｆ３の一端が共通接続されている。第１のフィルタ回路Ｆ１～Ｆ３は、それぞれ、下記の第１～第３の通過帯域ｆ１～ｆ３を有する。 The filter device 1 has a common terminal 2. One end of the first to third filter circuits F1 to F3 is commonly connected to the common terminal 2. The first filter circuits F1 to F3 have the following first to third passbands f1 to f3, respectively.
　ｆ１；ローバンドセルラー帯、６９９ＭＨｚ～９６０ＭＨｚ。 F1: Low band cellular band, 699 MHz to 960 MHz.
　ｆ２；ＧＰＳ、ＧＬＯＮＡＳＳ及びＢＥＩＤＯＵ帯、１５５９ＭＨｚ～１６０８ＭＨｚ。 F2: GPS, GLONASS and BEIDOU bands, 1559 MHz to 1608 MHz.
　ｆ３；ミドルバンドセルラー帯、１７００ＭＨｚ～２１７０ＭＨｚ。 F3: Middle band cellular band, 1700 MHz to 2170 MHz.
　第１のフィルタ回路Ｆ１は、ＬＣ共振器と音響共振子とを有する、ローパスフィルタである。なお、第１のフィルタ回路Ｆ１は、上記ローバンドセルラー帯である第１の通過帯域ｆ１を有するが、ローパスフィルタであるため、９６０ＭＨｚ以下の帯域の信号を通過させる。すなわち、６９９～９６０ＭＨｚのローバンドセルラー帯を通過させるように、第１の通過帯域ｆ１が設定されている。また、第２のフィルタ回路Ｆ２は、音響共振子からなるバンドパスフィルタであり、ラダー型フィルタからなる。 The first filter circuit F1 is a low-pass filter having an LC resonator and an acoustic resonator. The first filter circuit F1 has the first pass band f1 that is the low-band cellular band, but is a low-pass filter, and therefore passes signals in a band of 960 MHz or less. That is, the first pass band f1 is set so as to pass the low band cellular band of 699 to 960 MHz. The second filter circuit F2 is a bandpass filter made of an acoustic resonator, and is made of a ladder type filter.
　第３のフィルタ回路Ｆ３は、ＬＣ共振器と音響共振子とを有する、ハイパスフィルタである。第３のフィルタ回路Ｆ３はハイパスフィルタであり、上記第３の通過帯域ｆ３の下限である１７００ＭＨｚ以上の周波数の信号を通過させる。 The third filter circuit F3 is a high-pass filter having an LC resonator and an acoustic resonator. The third filter circuit F3 is a high-pass filter, and passes a signal having a frequency of 1700 MHz or higher which is the lower limit of the third passband f3.
　より詳細には、第１のフィルタ回路Ｆ１は、共通端子２と第１の端子３とを結ぶ第１の信号ライン４を有する。第１の信号ライン４に、複数の第１のインダクタ５ａ～５ｃが設けられている。複数の第１のインダクタ５ａ～５ｃは第１の信号ライン４において直列に接続されている。 More specifically, the first filter circuit F1 has a first signal line 4 connecting the common terminal 2 and the first terminal 3. A plurality of first inductors 5 a to 5 c are provided on the first signal line 4. The plurality of first inductors 5 a to 5 c are connected in series in the first signal line 4.
　第１のインダクタ５ａ～５ｃにそれぞれ並列に第１の容量素子６ａ～６ｃが接続されている。また、第１のインダクタ５ａと第１のインダクタ５ｂとの間の接続点とグラウンド電位との間に、インピーダンス調整用の第２の容量素子７ａが接続されている。第２の容量素子７ａはコンデンサからなる。インピーダンス調整用の第２の容量素子７ａと直列にインダクタ８が接続されている。また、第１のインダクタ５ｂと第１のインダクタ５ｃとの間の接続点とグラウンド電位との間に、第２の容量素子７ｂとして、第１の音響共振子が接続されている。 The first capacitive elements 6a to 6c are connected in parallel to the first inductors 5a to 5c, respectively. Further, a second capacitance element 7a for impedance adjustment is connected between a connection point between the first inductor 5a and the first inductor 5b and the ground potential. The second capacitive element 7a is a capacitor. An inductor 8 is connected in series with the second capacitor element 7a for impedance adjustment. A first acoustic resonator is connected as a second capacitive element 7b between a connection point between the first inductor 5b and the first inductor 5c and the ground potential.
　第２の容量素子７ｂとしての第１の音響共振子は、共振周波数と反共振周波数とを有する。本実施形態では、第２の容量素子７ｂは、弾性表面波共振子からなる。この弾性表面波共振子の容量性を利用して、第２の容量素子７ｂとして、弾性表面波共振子が用いられている。第１のインダクタ５ｃと第１の端子３との間の接続点とグラウンド電位との間に、第２の容量素子７ｃとして、第２の容量素子７ｂと同様の第１の音響共振子が接続されている。 The first acoustic resonator as the second capacitive element 7b has a resonance frequency and an anti-resonance frequency. In the present embodiment, the second capacitor element 7b is formed of a surface acoustic wave resonator. A surface acoustic wave resonator is used as the second capacitive element 7b by utilizing the capacitance of the surface acoustic wave resonator. A first acoustic resonator similar to the second capacitive element 7b is connected as the second capacitive element 7c between the connection point between the first inductor 5c and the first terminal 3 and the ground potential. Has been.
　上記のように、第１のフィルタ回路Ｆ１において、共通端子２に最も近い素子は、第１のインダクタ５ａである。第１のフィルタ回路Ｆ１においては、第２の容量素子７ａ～７ｃは、インピーダンス調整用の容量素子である。そして、２個の第２の容量素子７ｂ，７ｃが、上記のように第１の音響共振子からなり、この共振周波数は第２のフィルタ回路Ｆ２の通過帯域ｆ２に位置している。従って、第２のフィルタ回路Ｆ２の通過帯域の信号を、グラウンド電位側に逃がすことができる。 As described above, in the first filter circuit F1, the element closest to the common terminal 2 is the first inductor 5a. In the first filter circuit F1, the second capacitance elements 7a to 7c are impedance adjustment capacitance elements. The two second capacitive elements 7b and 7c are composed of the first acoustic resonator as described above, and the resonance frequency is located in the pass band f2 of the second filter circuit F2. Therefore, the signal in the pass band of the second filter circuit F2 can be released to the ground potential side.
　第２のフィルタ回路Ｆ２は、共通端子２と第２の端子９とを結ぶ第２の信号ライン１０を有する。第２の信号ライン１０において、共通端子２側から順に、直列腕共振子Ｓ１，Ｓ２，Ｓ３，Ｓ４，Ｓ５が設けられている。すなわち、第２の信号ライン１０は、直列腕を構成しており、この直列腕において、直列腕共振子Ｓ１～Ｓ５が直列に接続されている。上記直列腕共振子Ｓ１～Ｓ５は、弾性表面波共振子からなる。直列腕共振子Ｓ１～Ｓ５が共振周波数と、反共振周波数とを有する第２の音響共振子に相当する。 The second filter circuit F2 has a second signal line 10 connecting the common terminal 2 and the second terminal 9. In the second signal line 10, series arm resonators S1, S2, S3, S4, and S5 are provided in order from the common terminal 2 side. That is, the second signal line 10 constitutes a series arm, and the series arm resonators S1 to S5 are connected in series in this series arm. The series arm resonators S1 to S5 are composed of surface acoustic wave resonators. The series arm resonators S1 to S5 correspond to a second acoustic resonator having a resonance frequency and an anti-resonance frequency.
　直列腕共振子Ｓ１と直列腕共振子Ｓ２との間の接続点とグラウンド電位とを結ぶ並列腕に並列腕共振子Ｐ１が設けられている。直列腕共振子Ｓ２と直列腕共振子Ｓ３との間の接続点とグラウンド電位とを結ぶ並列腕に並列腕共振子Ｐ２が設けられている。直列腕共振子Ｓ３と直列腕共振子Ｓ４との間の接続点とグラウンド電位とを結ぶ並列腕に並列腕共振子Ｐ３が設けられている。直列腕共振子Ｓ４と直列腕共振子Ｓ５との間の接続点とグラウンド電位とを結ぶ並列腕に並列腕共振子Ｐ４が設けられている。上記並列腕共振子Ｐ１～Ｐ４もまた、弾性表面波共振子からなる。 The parallel arm resonator P1 is provided on the parallel arm connecting the connection point between the series arm resonator S1 and the series arm resonator S2 and the ground potential. The parallel arm resonator P2 is provided on the parallel arm that connects the connection point between the series arm resonator S2 and the series arm resonator S3 and the ground potential. The parallel arm resonator P3 is provided on the parallel arm that connects the connection point between the series arm resonator S3 and the series arm resonator S4 and the ground potential. A parallel arm resonator P4 is provided on the parallel arm connecting the connection point between the series arm resonator S4 and the series arm resonator S5 and the ground potential. The parallel arm resonators P1 to P4 are also composed of surface acoustic wave resonators.
　第２のフィルタ回路Ｆ２は、上記直列腕共振子Ｓ１～Ｓ５及び並列腕共振子Ｐ１～Ｐ４を有するラダー型フィルタである。第２のフィルタ回路Ｆ２は、バンドパスフィルタであり、その通過帯域の中心周波数は、前述した通過帯域ｆ２に位置している。 The second filter circuit F2 is a ladder filter having the series arm resonators S1 to S5 and the parallel arm resonators P1 to P4. The second filter circuit F2 is a band pass filter, and the center frequency of the pass band is located in the above-described pass band f2.
　直列腕共振子Ｓ１～Ｓ５の共振周波数は通過帯域ｆ２内に、並列腕共振子Ｐ１～Ｐ４の反共振周波数は通過帯域ｆ２内にある。 The resonance frequencies of the series arm resonators S1 to S5 are in the passband f2, and the antiresonance frequencies of the parallel arm resonators P1 to P4 are in the passband f2.
　第２のフィルタ回路Ｆ２においては、第２の信号ライン１０において、共通端子２に最も近い素子は、上記直列腕共振子Ｓ１である第２の音響共振子である。 In the second filter circuit F2, the element closest to the common terminal 2 in the second signal line 10 is the second acoustic resonator which is the series arm resonator S1.
　第３のフィルタ回路Ｆ３は、共通端子２と第３の端子１１とを結ぶ第３の信号ライン１２を有する。第３の信号ライン１２において、第３のフィルタ回路Ｆ３と第３の端子１１との間に、ローパスフィルタ２１が接続されている。 The third filter circuit F3 has a third signal line 12 connecting the common terminal 2 and the third terminal 11. In the third signal line 12, a low pass filter 21 is connected between the third filter circuit F 3 and the third terminal 11.
　第３のフィルタ回路Ｆ３はハイパスフィルタである。第３のフィルタ回路Ｆ３と、ローパスフィルタ２１とが直列に接続されており、従って、第３のフィルタ回路Ｆ３とローパスフィルタ２１とにより通過帯域が形成されている。 The third filter circuit F3 is a high-pass filter. The third filter circuit F3 and the low-pass filter 21 are connected in series. Therefore, the third filter circuit F3 and the low-pass filter 21 form a pass band.
　第３のフィルタ回路Ｆ３においては、第３の信号ライン１２上に第３の音響共振子１３ａ～１３ｃが設けられている。複数の第３の音響共振子１３ａ～１３ｃは、第３の信号ライン１２上において、互いに直列に接続されている。 In the third filter circuit F 3, third acoustic resonators 13 a to 13 c are provided on the third signal line 12. The plurality of third acoustic resonators 13 a to 13 c are connected to each other in series on the third signal line 12.
　第３の音響共振子１３ａと第３の音響共振子１３ｂとの間の接続点とグラウンド電位の間において第３のインダクタ１４ａと、第３の容量素子１５ａとが互いに直列に接続されている。同様に、第３の音響共振子１３ｂと第３の音響共振子１３ｃとの間の接続点とグラウンド電位との間において、第３のインダクタ１４ｂと第３の容量素子１５ｂとが直列に接続されている。 The third inductor 14a and the third capacitive element 15a are connected in series between the connection point between the third acoustic resonator 13a and the third acoustic resonator 13b and the ground potential. Similarly, the third inductor 14b and the third capacitive element 15b are connected in series between the connection point between the third acoustic resonator 13b and the third acoustic resonator 13c and the ground potential. ing.
　第３のフィルタ回路Ｆ３において、共通端子２に最も近い素子は、第３の音響共振子１３ａである。 In the third filter circuit F3, the element closest to the common terminal 2 is the third acoustic resonator 13a.
　フィルタ装置１においては、第１のフィルタ回路Ｆ１において、共通端子２に最も近い素子が第１のインダクタ５ａであり、第２のフィルタ回路Ｆ２及び第３のフィルタ回路Ｆ３の共通端子２に最も近い素子が、それぞれ第２，第３の音響共振子であり、かつこれらの素子が信号ライン上に配置されている。そのため、ＬＣフィルタからなる第１，第３のフィルタ回路Ｆ１，Ｆ３と、音響共振子を用いた第２のフィルタ回路Ｆ２との共通端子２側におけるインピーダンス整合回路を省略することができる。 In the filter device 1, in the first filter circuit F1, the element closest to the common terminal 2 is the first inductor 5a, and is closest to the common terminal 2 of the second filter circuit F2 and the third filter circuit F3. The elements are second and third acoustic resonators, respectively, and these elements are arranged on the signal line. Therefore, the impedance matching circuit on the common terminal 2 side of the first and third filter circuits F1 and F3 made of LC filters and the second filter circuit F2 using the acoustic resonator can be omitted.
　第３のフィルタ回路Ｆ３の第３の音響共振子１３ａ～１３ｃの反共振周波数は第２のフィルタ回路Ｆ２の通過帯域ｆ２に位置している。 The anti-resonance frequency of the third acoustic resonators 13a to 13c of the third filter circuit F3 is located in the pass band f2 of the second filter circuit F2.
　従って、第３のフィルタ回路Ｆ３のフィルタ特性において、通過帯域ｆ２にトラップを形成することができる。 Therefore, a trap can be formed in the pass band f2 in the filter characteristics of the third filter circuit F3.
　ローパスフィルタ２１は、第３の信号ライン１２上に設けられた第４のインダクタ２２ａ，２２ｂを有する。第４のインダクタ２２ａ，２２ｂに、それぞれ、第４の容量素子２３ａ，２３ｂが並列に接続されている。第４のインダクタ２２ａの第３のフィルタ回路Ｆ３側端部とグラウンド電位との間に、第５の容量素子２４ａが接続されている。また、第４のインダクタ２２ａと第４のインダクタ２２ｂとの間の接続点とグラウンド電位との間に、第５の容量素子２４ｂが接続されている。第４のインダクタ２２ｂと第３の端子１１との間の接続点とグラウンド電位との間に第５の容量素子２４ｃが接続されている。第５の容量素子２４ａ～２４ｃは、音響共振子からなり、共振周波数と反共振周波数とを有する。 The low-pass filter 21 includes fourth inductors 22 a and 22 b provided on the third signal line 12. Fourth capacitive elements 23a and 23b are connected in parallel to the fourth inductors 22a and 22b, respectively. A fifth capacitor 24a is connected between the end of the fourth inductor 22a on the third filter circuit F3 side and the ground potential. In addition, the fifth capacitive element 24b is connected between the connection point between the fourth inductor 22a and the fourth inductor 22b and the ground potential. A fifth capacitive element 24c is connected between the connection point between the fourth inductor 22b and the third terminal 11 and the ground potential. The fifth capacitive elements 24a to 24c are made of acoustic resonators and have a resonance frequency and an anti-resonance frequency.
　ローパスフィルタ２１は必ずしも設けられずともよいが、ローパスフィルタ２１を設けることにより、前述したように、通過帯域を形成することができる。 The low-pass filter 21 is not necessarily provided, but by providing the low-pass filter 21, a pass band can be formed as described above.
　好ましくは、第５の容量素子２４ａ～２４ｃの共振周波数を第２のフィルタ回路Ｆ２の通過帯域ｆ２に位置させることが望ましい。それによって、共通端子２と第３の端子１１との間のフィルタ回路において、第２の通過帯域における減衰量をより一層大きくすることができる。 Preferably, the resonance frequency of the fifth capacitive elements 24a to 24c is positioned in the pass band f2 of the second filter circuit F2. Thereby, in the filter circuit between the common terminal 2 and the third terminal 11, the attenuation in the second pass band can be further increased.
　好ましくは、音響共振子で構成される第２の容量素子７ｂ，７ｃ、第２のフィルタ回路Ｆ２で用いられている直列腕共振子Ｓ１～Ｓ５、並列腕共振子Ｐ１～Ｐ４及び第３のフィルタ回路Ｆ３で用いられている第３の音響共振子１３ａ～１３ｃ、第５の容量素子２４ａ～２４ｃを構成している音響共振子は、全て共振周波数及び反共振周波数がほぼ等しいことが望ましい。それによって、音響共振子の種類を削減することができ、コストの低減及びフィルタ装置１を構成する圧電基板等の共通化を図ることができる。よって、フィルタ装置１の小型化も図ることが可能となる。特に同じ圧電体を用いて、第１～第３のフィルタ回路Ｆ１～Ｆ３を構成することができる。 Preferably, the second capacitive elements 7b and 7c constituted by acoustic resonators, the series arm resonators S1 to S5, the parallel arm resonators P1 to P4, and the third filter used in the second filter circuit F2. It is desirable that all the acoustic resonators constituting the third acoustic resonators 13a to 13c and the fifth capacitive elements 24a to 24c used in the circuit F3 have substantially the same resonance frequency and antiresonance frequency. As a result, the types of acoustic resonators can be reduced, the cost can be reduced, and the piezoelectric substrate or the like constituting the filter device 1 can be shared. Therefore, the filter device 1 can be downsized. In particular, the first to third filter circuits F1 to F3 can be configured using the same piezoelectric body.
　好ましくは、第１のフィルタ回路の第２の容量素子が音響共振子からなり、第２のフィルタ回路が、直列腕である第２の信号ラインとグラウンド電位とを結ぶ並列腕を有し、並列腕に音響共振子が配置されており、第１のフィルタ回路の第２の容量素子を構成している音響共振子及び第２のフィルタ回路の並列腕に配置されている音響共振子の共振周波数が、第２の音響共振子の共振周波数とほぼ同じである。 Preferably, the second capacitive element of the first filter circuit is formed of an acoustic resonator, and the second filter circuit has a parallel arm that connects the second signal line, which is a serial arm, and a ground potential, and is connected in parallel. An acoustic resonator is arranged on the arm, and the resonance frequency of the acoustic resonator constituting the second capacitive element of the first filter circuit and the acoustic resonator arranged on the parallel arm of the second filter circuit Is substantially the same as the resonance frequency of the second acoustic resonator.
　より好ましくは、第２の音響共振子、第１のフィルタ回路の第２の容量素子を構成している音響共振子及び上記第２のフィルタ回路の並列腕に配置されている音響共振子の各共振周波数が、これらの音響共振子の共振周波数の平均値±５％の範囲内にある。 More preferably, each of the second acoustic resonator, the acoustic resonator constituting the second capacitive element of the first filter circuit, and the acoustic resonator disposed in the parallel arm of the second filter circuit The resonance frequency is in the range of the average value ± 5% of the resonance frequencies of these acoustic resonators.
　図２は、第１のフィルタ回路Ｆ１のフィルタ特性を示し、図３は第２のフィルタ回路のフィルタ特性を示し、図４は第３のフィルタ回路Ｆ３のフィルタ特性を示す。 2 shows the filter characteristics of the first filter circuit F1, FIG. 3 shows the filter characteristics of the second filter circuit, and FIG. 4 shows the filter characteristics of the third filter circuit F3.
　図２に示すように、第１のフィルタ回路では、第１の通過帯域ｆ１において減衰量が小さくなっている。これに対して、第２の通過帯域ｆ２及び第３の通過帯域ｆ３においては、減衰量が十分大きくされている。 As shown in FIG. 2, in the first filter circuit, the attenuation amount is small in the first pass band f1. In contrast, in the second passband f2 and the third passband f3, the amount of attenuation is sufficiently large.
　なお、第２の通過帯域ｆ２の下の矢印Ａは第１のフィルタ回路における第２の容量素子７ｂ，７ｃとして用いられている音響共振子の反共振周波数によるトラップの位置を示す。すなわち、第２の容量素子７ｂ，７ｃとしての音響共振子の反共振周波数が矢印Ａで示す周波数に位置するため、第２の通過帯域ｆ２における減衰量を十分大きくすることが可能とされている。 Note that an arrow A below the second passband f2 indicates the position of the trap due to the antiresonance frequency of the acoustic resonator used as the second capacitive elements 7b and 7c in the first filter circuit. That is, since the antiresonance frequency of the acoustic resonator as the second capacitive elements 7b and 7c is located at the frequency indicated by the arrow A, it is possible to sufficiently increase the attenuation in the second passband f2. .
　第１のフィルタ回路Ｆ１では、第２の容量素子７ａ～７ｃの内、第２の容量素子７ｂ，７ｃが音響共振子からなるが、少なくとも１個の第１の容量素子が音響共振子により構成されておればよい。 In the first filter circuit F1, among the second capacitive elements 7a to 7c, the second capacitive elements 7b and 7c are made of acoustic resonators, but at least one first capacitive element is made of an acoustic resonator. It only has to be done.
　図３に示すように、第２のフィルタ回路Ｆ２のフィルタ特性では、第２の通過帯域ｆ２の減衰量が十分に小さくされている。これに対して、第１の通過帯域ｆ１及び第３の通過帯域ｆ３では、十分大きな減衰量が得られている。この通過帯域は、第２のフィルタ回路Ｆ２のバンドパスフィルタとしての特性により得られている。 As shown in FIG. 3, in the filter characteristic of the second filter circuit F2, the attenuation amount of the second passband f2 is sufficiently small. In contrast, a sufficiently large attenuation is obtained in the first passband f1 and the third passband f3. This pass band is obtained by the characteristics of the second filter circuit F2 as a band pass filter.
　なお、バンドパスフィルタであるため、矢印Ｂで示す位置、すなわち通過帯域ｆ２内に、直列腕共振子Ｓ１～Ｓ５の共振周波数と、並列腕共振子Ｐ１～Ｐ４の反共振周波数とが位置している。さらに、矢印Ｃで示す周波数位置の特性は並列腕共振子Ｐ１～Ｐ４の共振周波数による減衰極を示す。矢印Ｄは、直列腕共振子Ｓ１～Ｓ５の反共振周波数による減衰極を示す。 Since it is a bandpass filter, the resonance frequency of the series arm resonators S1 to S5 and the antiresonance frequency of the parallel arm resonators P1 to P4 are located in the position indicated by the arrow B, that is, in the passband f2. Yes. Further, the frequency position characteristic indicated by the arrow C indicates the attenuation pole due to the resonance frequency of the parallel arm resonators P1 to P4. Arrow D indicates the attenuation pole due to the antiresonance frequency of the series arm resonators S1 to S5.
　直列腕共振子Ｓ１～Ｓ５と並列腕共振子Ｐ１～Ｐ４とを構成している音響共振子として全て同じものを用いているため、直列腕共振子Ｓ１～Ｓ５の共振周波数と、並列腕共振子Ｐ１～Ｐ４の反共振周波数とは矢印Ｂで示す位置とされている。 Since all the same acoustic resonators are used as the series arm resonators S1 to S5 and the parallel arm resonators P1 to P4, the resonance frequencies of the series arm resonators S1 to S5 and the parallel arm resonators are used. The antiresonance frequencies P1 to P4 are positions indicated by arrows B.
　もっとも、音響共振子からなる直列腕共振子Ｓ１～Ｓ５及び並列腕共振子Ｐ１～Ｐ４は、必ずしも共振周波数や反共振周波数がほぼ一致しておらずともよい。 However, the series arm resonators S1 to S5 and the parallel arm resonators P1 to P4 made of acoustic resonators do not necessarily have substantially the same resonance frequency and antiresonance frequency.
　図４に示すように、第３の通過帯域ｆ３において減衰量が十分に小さくされている。そして、第１の通過帯域ｆ１及び第２の通過帯域ｆ２では十分大きな減衰量が得られている。すなわちハイパスフィルタとしての特性により第１の通過帯域ｆ１における減衰量が十分大きくされている。他方、第２の通過帯域ｆ２における減衰量は、第３の音響共振子１３ａ～１３ｃの反共振周波数が矢印Ｅで示すように、通過帯域ｆ２に位置していることによる。それによって、第２の通過帯域ｆ２における減衰量を十分大きくすることが可能とされている。 As shown in FIG. 4, the attenuation is sufficiently small in the third passband f3. A sufficiently large attenuation is obtained in the first passband f1 and the second passband f2. That is, the attenuation amount in the first pass band f1 is sufficiently large due to the characteristics as a high-pass filter. On the other hand, the attenuation in the second pass band f2 is due to the antiresonance frequencies of the third acoustic resonators 13a to 13c being located in the pass band f2, as indicated by the arrow E. Thereby, it is possible to sufficiently increase the attenuation in the second passband f2.
　さらにローパスフィルタ２１が接続されているため、第３の通過帯域ｆ３よりも高域側においては減衰量が徐々に大きくなっている。加えて、第５の容量素子２４ａ～２４ｃとしての各音響共振子の共振周波数が矢印Ｆで示す周波数に位置する。そのため、第３の通過帯域ｆ３の高域側に矢印Ｆで示す周波数位置にトラップを形成することが可能とされている。よって、第３の通過帯域ｆ３の低域側及び高域側において、減衰量が十分大きなトラップを形成することができ、選択度を高めることが可能とされている。 Furthermore, since the low-pass filter 21 is connected, the amount of attenuation gradually increases on the higher frequency side than the third passband f3. In addition, the resonance frequency of each acoustic resonator as the fifth capacitive elements 24a to 24c is located at the frequency indicated by the arrow F. Therefore, it is possible to form a trap at the frequency position indicated by the arrow F on the high frequency side of the third passband f3. Therefore, traps with sufficiently large attenuation can be formed on the low frequency side and high frequency side of the third passband f3, and the selectivity can be increased.
　また、第５の容量素子２４ａ～２４ｃとしての音響共振子は、上記トラップを形成するために設けられているが、少なくとも１個の音響共振子が備えられておればトラップを形成することができる。 The acoustic resonators as the fifth capacitive elements 24a to 24c are provided to form the trap. However, if at least one acoustic resonator is provided, the trap can be formed. .
　なお、第３のフィルタ回路Ｆ３においては、第３の音響共振子１３ａ～１３ｃの内、共通端子２に最も近い第３の音響共振子１３ａを含んでおればよい。第３の音響共振子１３ｂ，１３ｃは省略されてもよい。 The third filter circuit F3 only needs to include the third acoustic resonator 13a closest to the common terminal 2 among the third acoustic resonators 13a to 13c. The third acoustic resonators 13b and 13c may be omitted.
　前述したように、第２の容量素子７ｂは、弾性表面波共振子により構成されていた。このような弾性表面波共振子の構造は特に限定されない。例えば、図７に示す弾性表面波共振子３１を用いることができる。弾性表面波共振子３１では、圧電基板３２上にＩＤＴ電極３３が設けられている。特に限定されないが、ＩＤＴ電極３３を覆うようにＳｉＯ２からなる誘電体膜３４が設けられている。この誘電体膜３４の膜厚や材質を調整することにより、前述した音響共振子の共振特性上の応答の大きさを調整することができる。また、ＩＤＴ電極を構成している金属や膜厚を調整することにより、共振周波数と反共振周波数との周波数位置を調整することもできる。 As described above, the second capacitor element 7b is formed of a surface acoustic wave resonator. The structure of such a surface acoustic wave resonator is not particularly limited. For example, a surface acoustic wave resonator 31 shown in FIG. 7 can be used. In the surface acoustic wave resonator 31, an IDT electrode 33 is provided on a piezoelectric substrate 32. Although not particularly limited, a dielectric film 34 made of SiO 2 is provided so as to cover the IDT electrode 33. By adjusting the film thickness and material of the dielectric film 34, the magnitude of the response on the resonance characteristics of the acoustic resonator described above can be adjusted. Moreover, the frequency position of the resonance frequency and the anti-resonance frequency can be adjusted by adjusting the metal constituting the IDT electrode and the film thickness.
　また、上記実施形態では、音響共振子として上記弾性表面波共振子を示したが、弾性表面波共振子以外の音響共振子を用いてもよい。例えば、弾性境界波共振子を用いてもよい。また、圧電薄膜を伝搬するバルク波を利用したＢＡＷ共振子を用いてもよい。さらに、単一の圧電基板または積層型圧電体を用いた圧電共振子を用いてもよい。 In the above embodiment, the surface acoustic wave resonator is shown as an acoustic resonator. However, an acoustic resonator other than the surface acoustic wave resonator may be used. For example, a boundary acoustic wave resonator may be used. A BAW resonator using a bulk wave propagating through the piezoelectric thin film may be used. Furthermore, a piezoelectric resonator using a single piezoelectric substrate or a laminated piezoelectric material may be used.
　図５は、本発明の第２の実施形態に係るフィルタ装置の回路図である。第１のフィルタ回路Ｆ１では第１の容量素子６ａ～６ｃが音響共振子からなる。また、第１のインダクタ５ａと第１のインダクタ５ｂとの間の接続点とグラウンド電位との間には、音響共振子からなる第２の容量素子７ｄが接続されている。 FIG. 5 is a circuit diagram of a filter device according to the second embodiment of the present invention. In the first filter circuit F1, the first capacitive elements 6a to 6c are acoustic resonators. A second capacitive element 7d made of an acoustic resonator is connected between a connection point between the first inductor 5a and the first inductor 5b and the ground potential.
　さらに、第３のフィルタ回路Ｆ３において、第３の容量素子１５ｃ，１５ｄが音響共振子からなる。その他の構成は、フィルタ装置４１はフィルタ装置１と同様に構成されている。 Furthermore, in the third filter circuit F3, the third capacitive elements 15c and 15d are made of acoustic resonators. In other configurations, the filter device 41 is configured in the same manner as the filter device 1.
　上記のような、第１の容量素子６ａ～６ｃを音響共振子により構成してもよく、第１のフィルタ回路Ｆ１において、第１の信号ライン４とグラウンド電位とを結ぶ線路に配置される容量素子を全て音響共振子としてもよい。 The first capacitive elements 6a to 6c as described above may be constituted by acoustic resonators, and in the first filter circuit F1, capacitors arranged on the line connecting the first signal line 4 and the ground potential. All the elements may be acoustic resonators.
　また、第３のフィルタ回路Ｆ３においても図５に示すように、第３の信号ライン１２とグラウンド電位とを結ぶ線路に、第５の容量素子２４ａ～２４ｃとして音響共振子を用いてもよい。音響共振子の容量を用いることにより、フィルタ装置４１は、フィルタ装置１と同様の作用効果を奏する。 Also in the third filter circuit F3, as shown in FIG. 5, acoustic resonators may be used as the fifth capacitive elements 24a to 24c on the line connecting the third signal line 12 and the ground potential. By using the capacitance of the acoustic resonator, the filter device 41 has the same effects as the filter device 1.
　加えて、音響共振子を用いた場合、第３の信号ライン１２に接続されている音響共振子では、反共振周波数を第２の通過帯域ｆ２に位置させることにより、第２の通過帯域ｆ２における減衰量の拡大を図ることができる。また、第３の信号ライン１２とグラウンド電位とを結ぶ線路に設けられる音響共振子では、反共振周波数を第２の通過帯域ｆ２に位置させることにより、第２の通過帯域ｆ２における減衰量をさらに大きくすることができる。 In addition, when an acoustic resonator is used, in the acoustic resonator connected to the third signal line 12, the anti-resonance frequency is positioned in the second pass band f2, so that the second resonator in the second pass band f2 The amount of attenuation can be increased. In the acoustic resonator provided on the line connecting the third signal line 12 and the ground potential, the attenuation in the second passband f2 is further increased by positioning the antiresonance frequency in the second passband f2. Can be bigger.
　図６は、第３の実施形態に係るフィルタ装置５１の回路図である。第３の実施形態のフィルタ装置５１では、第１及び第２のフィルタ回路Ｆ１，Ｆ２は、第２の実施形態のフィルタ装置４１と同様に構成されている。異なるところは、第３のフィルタ回路Ｆ３がラダー型フィルタからなるバンドパスフィルタであることにある。 FIG. 6 is a circuit diagram of the filter device 51 according to the third embodiment. In the filter device 51 of the third embodiment, the first and second filter circuits F1, F2 are configured in the same manner as the filter device 41 of the second embodiment. The difference is that the third filter circuit F3 is a band-pass filter composed of a ladder filter.
　すなわち、共通端子２と第３の端子１１とを結ぶ第３の信号ライン１２上に、直列腕共振子Ｓ１１～Ｓ１５が互いに直列に接続されている。そして、直列腕共振子Ｓ１１，Ｓ１２間の接続点とグラウンド電位とを結ぶ並列腕に、並列腕共振子Ｐ１１が設けられている。直列腕共振子Ｓ１２，Ｓ１３間の接続点とグラウンド電位との間に、並列腕共振子Ｐ１２が設けられている。直列腕共振子Ｓ１３，Ｓ１４間の接続点とグラウンド電位との間に、並列腕共振子Ｐ１３が設けられている。直列腕共振子Ｓ１４，Ｓ１５間の接続点とグラウンド電位とを結ぶ並列腕に、並列腕共振子Ｐ１４が設けられている。 That is, the series arm resonators S11 to S15 are connected in series on the third signal line 12 connecting the common terminal 2 and the third terminal 11. A parallel arm resonator P11 is provided on the parallel arm connecting the connection point between the series arm resonators S11 and S12 and the ground potential. A parallel arm resonator P12 is provided between the connection point between the series arm resonators S12 and S13 and the ground potential. A parallel arm resonator P13 is provided between the connection point between the series arm resonators S13 and S14 and the ground potential. A parallel arm resonator P14 is provided on the parallel arm connecting the connection point between the series arm resonators S14 and S15 and the ground potential.
　また、直列腕共振子Ｓ１１と直列腕共振子Ｓ１２との間の接続点とグラウンド電位との間に、インダクタ５２ａが接続されている。直列腕共振子Ｓ１４と直列腕共振子Ｓ１５との間の接続点とグラウンド電位との間に、インダクタ５２ｂが接続されている。インダクタ５２ａ，５２ｂは、インピーダンスを調整するために設けられている。 Further, an inductor 52a is connected between the connection point between the series arm resonator S11 and the series arm resonator S12 and the ground potential. An inductor 52b is connected between a connection point between the series arm resonator S14 and the series arm resonator S15 and the ground potential. The inductors 52a and 52b are provided to adjust the impedance.
　フィルタ装置５１のように、第３のフィルタ回路Ｆ３はそれ自身がバンドパスフィルタであってもよい。 Like the filter device 51, the third filter circuit F3 itself may be a bandpass filter.
　直列腕共振子Ｓ１１～Ｓ１５及び並列腕共振子Ｐ１１～Ｐ１４は、共振周波数と反共振周波数とを有する音響共振子からなる。フィルタ装置５１において、第３のフィルタ回路Ｆ３における共通端子２に最も近い素子は、直列腕共振子Ｓ１１である。すなわち、共通端子２に最も近い素子は第３の音響共振子であり、かつ第３の信号ライン１２上に設けられている。 The series arm resonators S11 to S15 and the parallel arm resonators P11 to P14 are acoustic resonators having a resonance frequency and an antiresonance frequency. In the filter device 51, the element closest to the common terminal 2 in the third filter circuit F3 is the series arm resonator S11. That is, the element closest to the common terminal 2 is the third acoustic resonator and is provided on the third signal line 12.
　フィルタ装置５１においても、第１のフィルタ回路Ｆ１において共通端子２に最も近い素子は、第１の信号ライン４に設けられた第１のインダクタ５ａであり、第２及び第３のフィルタ回路Ｆ２，Ｆ３においては、音響共振子からなる直列腕共振子Ｓ１，及び直列腕共振子Ｓ１１であり、それぞれ第２及び第３の信号ライン１０，１２上に設けられている。よって、共通端子２側において、インピーダンス整合回路を設ける必要はない。そのため、フィルタ装置５１においても、小型化及び低コスト化を果たすことができる。 Also in the filter device 51, the element closest to the common terminal 2 in the first filter circuit F1 is the first inductor 5a provided in the first signal line 4, and the second and third filter circuits F2, F2 are provided. In F3, there are a series arm resonator S1 and a series arm resonator S11 made of acoustic resonators, which are provided on the second and third signal lines 10 and 12, respectively. Therefore, it is not necessary to provide an impedance matching circuit on the common terminal 2 side. Therefore, the filter device 51 can also be reduced in size and cost.
　なお、本発明において、上記第１～第３のフィルタ回路Ｆ１～Ｆ３は適宜の第１～第３の実施形態からも明らかなように適宜変形することができる。すなわち、第１～第３のフィルタ回路Ｆ１～Ｆ３におけるフィルタ回路の段数や素子数は、実施形態の内容に限定されるものではない。 In the present invention, the first to third filter circuits F1 to F3 can be appropriately modified as will be apparent from appropriate first to third embodiments. That is, the number of filter circuits and the number of elements in the first to third filter circuits F1 to F3 are not limited to the contents of the embodiment.
１…フィルタ装置
２…共通端子
３…第１の端子
４…第１の信号ライン
５ａ～５ｃ…第１のインダクタ
６ａ～６ｃ…第１の容量素子
７ａ～７ｄ…第２の容量素子
８…インダクタ
９…第２の端子
１０…第２の信号ライン
１１…第３の端子
１２…第３の信号ライン
１３ａ～１３ｃ…第３の音響共振子
１４ａ，１４ｂ…第３のインダクタ
１５ａ～１５ｄ…第３の容量素子
２１…ローパスフィルタ
２２ａ，２２ｂ…第４のインダクタ
２３ａ，２３ｂ…第４の容量素子
２４ａ～２４ｃ…第５の容量素子
３１…弾性表面波共振子
３２…圧電基板
３３…ＩＤＴ電極
３４…誘電体膜
４１…フィルタ装置
５１…フィルタ装置
５２ａ，５２ｂ…インダクタ
Ｆ１～Ｆ３…第１～第３のフィルタ回路
Ｐ１～Ｐ４…並列腕共振子
Ｓ１～Ｓ５…直列腕共振子
Ｐ１１～Ｐ１４…並列腕共振子
Ｓ１１～Ｓ１５…直列腕共振子 DESCRIPTION OF SYMBOLS 1 ... Filter apparatus 2 ... Common terminal 3 ... 1st terminal 4 ... 1st signal line 5a-5c ... 1st inductor 6a-6c ... 1st capacitive element 7a-7d ... 2nd capacitive element 8 ... Inductor 9 ... 2nd terminal 10 ... 2nd signal line 11 ... 3rd terminal 12 ... 3rd signal line 13a-13c ... 3rd acoustic resonator 14a, 14b ... 3rd inductor 15a-15d ... 3rd Capacitor 21 ... low pass filters 22a and 22b ... fourth inductors 23a and 23b ... fourth capacitors 24a to 24c ... fifth capacitor 31 ... surface acoustic wave resonator 32 ... piezoelectric substrate 33 ... IDT electrode 34 ... Dielectric film 41 ... Filter device 51 ... Filter devices 52a and 52b ... Inductors F1 to F3 ... First to third filter circuits P1 to P4 ... Parallel arm resonators S1 to S5 ... Series arm resonators P11 to P14 ... Column arm resonators S11 ~ S15 ... the series arm resonator

Claims (11)

  1. 　共通端子と、
    　前記共通端子に接続されている第１の信号ラインを有しており、第１の通過帯域を有するローパスフィルタである第１のフィルタ回路と、
    　前記共通端子に接続されている第２の信号ラインを有しており、前記第１のフィルタ回路の前記第１の通過帯域よりも高域側に位置している第２の通過帯域を有しており、バンドパスフィルタである第２のフィルタ回路と、
    　前記共通端子に接続されている第３の信号ラインを有しており、前記第２のフィルタ回路の前記第２の通過帯域よりも高域側に位置している第３の通過帯域を有する第３のフィルタ回路と、
    を備え、
    　前記第１のフィルタ回路が、前記第１の信号ラインにおいて、前記共通端子に最も近くに配置されている第１のインダクタと、前記第１のインダクタと並列に接続されてＬＣ共振回路を構成している第１の容量素子とを含んでおり、
    　前記第２のフィルタ回路が、前記第２の信号ラインにおいて、前記共通端子に最も近くに配置されている第２の音響共振子を含んでおり、
    　前記第３のフィルタ回路が、前記第３の信号ラインにおいて、前記共通端子に最も近くに配置されている第３の音響共振子を含んでいる、フィルタ装置。     A common terminal,
    A first filter circuit having a first signal line connected to the common terminal and being a low pass filter having a first passband;
    A second signal line connected to the common terminal; and a second passband located on a higher frequency side than the first passband of the first filter circuit. A second filter circuit that is a bandpass filter;
    A third signal line having a third signal line connected to the common terminal and having a third pass band located on a higher frequency side than the second pass band of the second filter circuit; 3 filter circuits;
    With
    The first filter circuit is connected in parallel with the first inductor disposed closest to the common terminal in the first signal line, and constitutes an LC resonance circuit. A first capacitive element that includes:
    The second filter circuit includes a second acoustic resonator disposed in the second signal line closest to the common terminal;
    The filter device, wherein the third filter circuit includes a third acoustic resonator arranged closest to the common terminal in the third signal line.
  2. 　前記第１のフィルタ回路が、反共振周波数と前記第２の通過帯域内に位置する共振周波数とを有する第１の音響共振子と、前記第１の信号ラインとグラウンド電位とに接続される第２の容量素子とを含んでいる、請求項１に記載のフィルタ装置。 The first filter circuit is connected to a first acoustic resonator having an anti-resonance frequency and a resonance frequency located in the second passband, and to a first signal line and a ground potential. The filter device according to claim 1, comprising two capacitive elements.
  3. 　前記第１のフィルタ回路の前記第２の容量素子が音響共振子からなり、
    　前記第２のフィルタ回路が、直列腕である第２の信号ラインとグラウンド電位とを結ぶ並列腕を有し、前記並列腕に音響共振子が配置されており、
    　前記第１のフィルタ回路の前記第２の容量素子を構成している前記音響共振子及び前記第２のフィルタ回路の前記並列腕に配置されている音響共振子の共振周波数が、前記第２の音響共振子の共振周波数とほぼ同じである、請求項２に記載のフィルタ装置。     The second capacitive element of the first filter circuit comprises an acoustic resonator;
    The second filter circuit has a parallel arm connecting a second signal line as a series arm and a ground potential, and an acoustic resonator is disposed in the parallel arm;
    The acoustic resonator disposed in the parallel arm of the acoustic resonator constituting the second capacitive element of the first filter circuit and the second filter circuit has a resonance frequency of the second The filter device according to claim 2, wherein the filter device is substantially the same as a resonance frequency of the acoustic resonator.
  4. 　前記第２の音響共振子、前記第１のフィルタ回路の前記第２の容量素子を構成している前記音響共振子及び前記第２のフィルタ回路の前記並列腕に配置されている音響共振子の各共振周波数が、これらの音響共振子の共振周波数の平均値±５％の範囲内にある、請求項３に記載のフィルタ装置。 The second acoustic resonator, the acoustic resonator constituting the second capacitive element of the first filter circuit, and the acoustic resonator disposed on the parallel arm of the second filter circuit. The filter device according to claim 3, wherein each resonance frequency is within a range of an average value ± 5% of resonance frequencies of these acoustic resonators.
  5. 　前記第２のフィルタ回路が、前記第２の音響共振子と、前記第２の信号ラインとグラウンド電位とを接続している並列腕に設けられた第４の音響共振子とを有する、ラダー型フィルタである、請求項１～４のいずれか１項に記載のフィルタ装置。 The ladder type, wherein the second filter circuit includes the second acoustic resonator and a fourth acoustic resonator provided on a parallel arm connecting the second signal line and a ground potential. The filter device according to any one of claims 1 to 4, wherein the filter device is a filter.
  6. 　前記第３のフィルタ回路が、前記第３の信号ラインとグラウンド電位との間に接続された第２のインダクタと、該第２のインダクタと直列に接続された第３の容量素子とを有するＬＣフィルタである、請求項１～５のいずれか１項に記載のフィルタ装置。 The third filter circuit includes a second inductor connected between the third signal line and a ground potential, and an LC having a third capacitor connected in series with the second inductor. The filter device according to any one of claims 1 to 5, wherein the filter device is a filter.
  7. 　前記第３のフィルタ回路がバンドパスフィルタである、請求項１～５のいずれか１項に記載のフィルタ装置。 The filter device according to any one of claims 1 to 5, wherein the third filter circuit is a band-pass filter.
  8. 　前記第３のフィルタ回路がラダー型フィルタである、請求項７に記載のフィルタ装置。 The filter device according to claim 7, wherein the third filter circuit is a ladder type filter.
  9. 　前記第１～第３の音響共振子の少なくとも１つが、弾性波共振子である、請求項２～８のいずれか１項に記載のフィルタ装置。 The filter device according to any one of claims 2 to 8, wherein at least one of the first to third acoustic resonators is an elastic wave resonator.
  10. 　前記弾性波共振子が弾性表面波共振子である、請求項９に記載のフィルタ装置。 The filter device according to claim 9, wherein the acoustic wave resonator is a surface acoustic wave resonator.
  11. 　前記第１の容量素子が、音響共振子からなる、請求項１～１０のいずれか１項に記載のフィルタ装置。 The filter device according to any one of claims 1 to 10, wherein the first capacitive element is formed of an acoustic resonator.
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